Piston



April 1, 1941.

J. FLAMMAN'G PISTON Filed Feb.

Patenvted Apr. 1, 1941 UNITED STAT-Es PATENT OFFICE PISTON tion oi'Delaware Application February 15, 1937, serial No. 125,756 1 claim. (ci.sos-11) This invention pertains to pistons and more particularly totrunk type istons constructed of thermo-expansible metall, such asaluminum, or its alloys, magnesium and the like, having a highcoemciency of thermal expansion.

One of the objects of this invention'is to provide a piston of thecharacter described which will function in a cylinder through variousranges of temperature and compensate automatically for expansion.

Further objects will appear from thefollowing description taken inconnection 'with the accompanying drawing, in which:

Figure 1 is a side view illustrating one form of piston to which thisinvention may be applied.

Figure 2 is a longitudinal section through the wrist pin axis of thepiston shown in Figure l.

Figure 3 is a sectional view of an engine cylinder illustrated with apiston therein constructed in accordance with this invention, saidpiston being seen in bottom view, and

Figure 4 is a fragmentary side view similar to Figure l, illustratinganother form of piston to which this invention may be applied.

Referring to the drawing the piston comprises a head i and askirtindicated generally at `2. Wrist pin bosses 3 are provided. Thesebosses are connected to the head I by a sti structure including one ormore longitudinal ribs il extending from the upper portion of each wristpin boss to the inner side of the head. Similarly, one or morereinforcing ribs may be arranged to extend across the head on theinterior thereof. The structure thus described including the head, theribs d andl the wrist pin bosses Tis made stiff and rigid so as toprovide a. strong frame structure adapted to deliver the thrust of thegas explosion to the connecting rod.

'I'he skirt 2 is separated from the head l adjacent the two thrustfaces. The thrust face which takes the thrust of the power stroke, shownin interior view in Figure r2, may or may not be separated from theheady by a horizontal slot or gap 6. This face is solid or uncutlongitudinally, while the opposite face, shown in Figure 1, is separatedfrom the head l by a slotA or gap 1, and

in addition is cut by a longitudinal slot l. extend-V ing up" into andcommunicatingwith the gap 1. In some cases it may be desirable to extendthe the regions of the thrust faces and the -skirt is webs i4 connectingthe skirt with the bosses. In

orderto `provide still more ample relief at the top, the relievedportions may be extended from the yregions opposite the bosses-aroundtoward one or both thrust faces so 'as to approach, to a greater or lessextent, the bearing axis of the bearing or thrust face. In the form ofpiston illustrated in the drawing this relieved portion is formed toapproach more closely, to the bearing axis at the head end of the skirtthan therebelow, thereby providing the so-called Keystone relief.

A bridge il spans the slot preferably just below the circumferentialslot l. The middle portion ofthis bridge is relatively thin so as to becomparatively flexible, while each end of the bridge has an anchorage i2having an extended connection with the skirt on the inside and,therefore, relatively rigid. A gap I3 may be provided in the bridge, andthis gap as well as the bridge 3o itself, is formed in the casting whenmade in the 35 skirt at the top. In the complete piston, therefore, thecorners I0 will be supported.

The piston is made in theusual manner .with the head-provided with theusual ring grooves il of smaller diameter than the'skirt. This skirt 40may alsobe given the usual taper so as to be slightly smaller at the topthan at the bottom.`

When such a piston is placed in the cylinder and subjected to the heatof the gases, the head will, of course, expand radially in alldirections.

This radial expansion of the head is transmitted to the skirt only inthe regions of the wrist pin bosses where, however. the skirt isrelievedto permit such expansion. Such radial expansion of the head is nottransmitted to the region of slot 8 clear to the open end of the pistonskirt 50 the thrust face between the bosses, because of as shown inFigure l. In other cases this slot ,f may beterminated at a point l asshown in Figure 4, short of the open end of the skirt. l

This cutting of the circumferential slot or slots the isolation broughtabout by the circumferential slot.l vAs a result. therefore, theisolated thrust tace ls drawn in so as to compensate for expension onthat diameter, while expansion along in the piston isolates the skirtfrom the head in the line oi' the wrist pin bosses has been compensatedfor by the relief. Such drawing in of the thrust face is permittedbecause of the bridge which, however, prevents undue ilexure of theskirt at the top, particularly at the corner and, therefore, insuresquiet operation. It will be understood that where the head is alsoisolated from the skirt at the unslotted face, there will be a drawingin on that face also as expension takes place along the line of thebosses.

It will be obvious that various changes may be made in the details ofconstruction, within the scope of the appended claim, without departingfrom the spirit of this invention. It is understood, therefore, that theinvention is not limited to the specific details shown or described.

Having thus described the invention, what is claimed is:

A trunk piston of thermo-expansible material having a head, a skirt, andwrist pin bosses connected to the head, said skirt havingcylinderbearing thrust faces and having relieved areas adjacent saidwrist pin bosses and between said thrust faces to permit thermalexpansion in the direction of the wrist pin axis, one of said thrustfaces being separated from the head by a slot extending horizontallybetween said relieved areas adjacent the top of the skirt, said thrustface having another slot extending vertically and y medially thereofdownwardly from said horizontal slot defining separate bearing cornersadjacent the junction of said horizontal and vertical slots, and abridge member anchored interiorly to the respective bearing corners andbridging the vertical slot adjacent the horizontal slot, and interioranchorage between said bridge and the respective bearing corners beingcircumferentially extended substantially across the thrust face. saidbridge member being constructed and arranged4 to prevent undue fiexureof the separate bearing corners.

JOHN FLALMANG.

